Nikkei falls for 2nd day on Wall Street; Hitachi gains on mid-term plan

* Hitachi up on higher operating margin forecast * Machinery data suggests companies' risk averse stance - analyst By Ayai Tomisawa TOKYO, May 17 (Reuters) - The Nikkei share average fell for a second day on Friday as caution over the recent steep rises continued to spur profit-taking while a pullback in Wall Street soured investor sentiment, but ongoing optimism in the benefits of a weak yen kept the index near the 15,000 mark. The Nikkei shed 0.3 percent to 14,992.83 in mid-mo